System of motor control.



R B., RAB

SYSTEM 0F MOTGR CONTROL.

APPLICATION 1111.211 mima, 1910.

' zen of the United States, residing at. Boston,

` at slow speed, and will exert a high torque ``motors i, nd their loads are then accelerated by gradually cutting out the groups of turns UNITED STATES PATENT oEEicE.

FRANK B. RAE, 0F BOSTON, MASSACHUSETTS.

SYSTEM OF MOTOR CONTROL.

Specification ot Letters Patent.

Patented Nov. 15, 1910.

To all whom it may concern:

Be it known that I, FRANK B. RAE, a citiin the county of Suffolk and State of Massachusetts, have invented certain new and 'useful Improvements in Systems of Motor Control, of which the following is a full, clear, and exact specilication.

This invention relates to system of motor control.I and has particular reference to the control of two or more electric motors by a single controller, as tor the operation of street cars or other electrically propelled cars. Y

Haile the invention may be used with any source of current, it is particularly adapted to the`control of motors operated by storage batteries, which latter require that the maximum current be within the safe discharge rate.

The motors are preferably of the multipole inter-pole type Series Wound, wherein the field windings consist of a plurality of groups of coils, one coil of each group being upon each pole-piece, and each group being controllable as a unit to vary the motor speed. Such a motor and method of control. result in a system attaining the highest economy in the use of currentduring the period of starting and accelerating the niotor with a maximum torque, and with sparkless commutation. F or this purpose, I use a very large number of turns upon the eld magnets which connected in series have a high ohmic "resistance, permitting a relatively small current to pass through the entire motor circuit but giving the maximum excitation and a saturated eld, while the armature current is reduced to just the ainperes necessary to produce the required starting effort. To prevent armature 'reaction at this time, I employ series inter-poles of relatively high magnetic strength, and thereby prevent any shifting of the point of commutation, the motors running sparkless under all variations or conditions of field magnetization. Under this maximum condition of field magnetization, the armatures will produce the necessary counter potential capable of starting the motors from restwith full load, with a small current. The

on the eld magnets, thus reducing the effective turns, and consequently the eld magnetization until maximum speed is attained.

In carrying out the invention, I have provided a method and apparatus whereby the motors and all windings are first connected in series with each other and the source; then speeded `up by reducing the effective magnetizing field turns; then connected in multiple with the source without opening the circuit or materially increasing the. current flow, by reinserting the field windings preiviously removed; and lastly increasing the speed by again reducing the effective magnetizing turns on each motor.

The invention will be more fully understood in connection" with the description of the accompanying drawing which shows diagrammatically an embodiment of the invention.

1 is a reversing controller of the usual type used for street railway controllers in which the upper set of contacts are revolved to reverse the armature current in motor A and the lower contacts to reverse the arrnature circuitin motor B; 2-2 are developed rings upon a short cylinder, their ends being separated by an air space; 3-3, lr-4', 5--5 are stationary contact segments of a disk, supported from the frame of the controller through the center of which the controller handle, attached to the insulated cylinder of supports for 2-2, passes. Contacts 6-'7-8-9-10-114-12-13-14r- 15--16-l-17--18 and 6 -7'-8-9 10'- 11'-12-13-l4-1516-1718 and also are segments supported upon insulated disks. Contacts 19-19 are supported upon an insulatin arm attached to the shaft 'of the control er, upon which are mounted the supports for the contact plates 2-2, and these contacts 19--19 serve to make electrical connection between the stationary plates 3-4--5, 3-4` 5 and the contact segments 6 to l18 and 6 to 18.

As will be explained, 20-21-22-23 are stationary contact-s, in such relation that when the controller cylinder, supportn the contact. rings 2-2, is turned in the irection of the arrow,electrical connection is made between contacts 20-21 through plate 2 and from contact 252-23 through plate 2".

A, B, are 4electric motors, having interpole 'magnets and sectional windings upon the main field magnets.

The coils F F1 F2 tFS are in circuit at all a a 1 a running positions, and consist of a relatively small number ot turns of coarse wire, having low resistance. 'lhe coils F4, F5, F, F1, 'consist of more turns ot tiner wire of greater resistance, the. coils FS, F, F1, F11. of still more turns of still liner wire and' greater the counter potential of the motor to such.

amount as will be within the nor-mal discharge rate of the supply battery. As the controller progressivelyT reduces the field` magnetizing turns, the ohmic resistance also diminishes, thereby somewhat increasing the current flow through the whole circuit, and thus varying the'interpole magnetization to secure sparkless commutation at ditferent speeds and loads.

The object of this invention is to produce a. controller for two motors of this type, and to further eti'ect the economy of operation by first connecting the two motors in series with the source of electrical supply cutting out certain of the coils to bringthe motor up to a certain speed, and then to connect the motors in parallel with the source of supply, and simultaneously therewith. reintroduce into each motor circuit all ot these windings or coils, then to further increase the speed of the motors by again successively cutting out'y the coils and progressive groups of coils until maximum speed is obtained.

tetex-ring now to the drawing and assaining that the reversing switch has been turned in the direction ot' thc arrow until the contact. rings thereon bear upon the stationary contacts shown and lett ,1n this position, and then aI-'slnning that the controller lever hasl been moved to bring the contact plate 2 in electrical connection with the stationary contacts Q0 and Q1 and the. plate 2 in contact with .12 and f-- and the. circuits may then be traced as `follows: -i'rom the battery to contact. l plate Q, 'contact 20, wire. 2l, through the lower reversing switch to wire 25, through the inter-pole coils tao l'notor B. through armature (t, wire 26.

through lower reversing switch to wire 27, through field coil F-FMF-FtL-lN-Fi- F1- F1- F'-- F" F1"-- F'1 F12 F13 F1-F1 to wire 28, branch wire 29 to contact (3" through brush contact 19 to ,st at ionary contact 5', by wire 30 to stationary contact 5, brush contact 19', stationary contact 6^, wire 31 to wire 3Q, thence through all of the tield indulgel ot motor to wire 32S, through the contacts and-platesnn the upper part of the reversing switch through wire to the armature and inter-pole coils of motor A again through the reversing switchI through wires 35 and 25o, thence to Contact 23, movable plate 2 to contact. 22 and thence to the battery, completing a circuit of both motors in series through all of their windings. It now the controller handle is moved farther in the direction ot' the arrow, contact is constantly maintained between stat-ionary Contactl 2t) and 21, through plate 2 and between 22 and L13, through plate 2', while the movable brush contactsn 19 and 19 are rotated until the Contact 19 connects the late 5 with the contact 8 and the brusl 19 connects the plate 5 with-the con- 'tact 8*. The circuit may then be traced as before through the tield coils to and includinfr F1, thence by wire 37 and 38 to contact 8 brush 19, Contact 5', wire tit) to plate 5 to brush 19', contact 8^ thence through the motor A by wire 39 and 40, thence to wire 3o and back to the battery. In this position of the controller. contacts 19 and 19', it will .be seen that the Held coils F14 andi"15 on motor B and similar coils on motor A are removed from the circuit.

Without tracing the circuit for each successive movement of the controller, it will be understood that one or more coils 'of each motor are successively cut out, as the contact brushes 19 and 19 are moved still farther in the direction of the arrows. When these brushes 19 and 19' have progressed until brush 19 connects the segment Lt with the segment 6, and brush 19 connects 4 and 6 then circuit may be traced as follows:- from the battery to contact 21, plate 2, contact 20, wire 24 through the lower reversing switch contacts and the inter-pole coils and armature of motor B to wire T successively to all of the field coils of motor l to wire E28,

Contact plate (i, brush 19, contact 4 through the resistance R to Contact plate 3', wire ft2 to contact 23, plate 2, contact 22 to the opposite pole of the battery, thus placing the motor B directly across the. battery terminal, but having resistance R interposed in its eireuit. ln the same manner, the circuit may be traced to contact 22, plate Q', contact Q3 to wire 43, thence through the upper reversing switch and the motor'A to contactl ti through brush 19', contact plate 4', resistance R to contact 3, thence by Wire 41 to contact 20, plate 2, contact-21 to the opposite side of the battery. Both motors are now in parallel withthe resistances interposed in their circuit, whileall of the field windings of cach motor are again included in the rcspective circuit of cach motor. A further movement of the controller handle carries the brush contacts 19 and 19 until they rest upon contact 3* and contact plate-6 and upon contact plate ti and contact plate B, in which position -the resistance It and R are removed from 'the circuit and both ot the motors are now in parallel with all of their coils in series respectively and without eX- ternal resistance, which has been interposed for the purpose of preventing excessive rise in the current of either machine at the instant the change is made from series to par allel connection. Continued movement of the controller handle, whereby the brushes 19 and '19 are moved forward in the direction of the arrow, will cut out the field coils of each motor, as may be readily traced on the diagram without, following the circuit through for each particular connection 'until brushes 19 and 19 finally connect the segments 18 with 3 and 18 with 3 when all of the coils and groups ot' coils have been removed from theV circuit or each motor ex cept coils F*F1-F2F3-, which are the coils producing the maximum speed -of the motor.

This invention is intended to provide a.

simple .means of controlling two motors,1

particularly for the operation of street cars and it will be readily understood that it' itr be desired to operate four motors that a duplicate set of contacts could be incorporated in one controlling case operated by one controller handle. This motor and method of control is also adapted to the operation of heavy automobile trucks in which cach motor drives a separate wheel, thereby dispensing with counter-shafts, gears, diti'erential, etc.

Having thus described my invention, what l' claim as new and desire to secure by Letters Patent isi. The combination with a plurality ot series motors, cach having field windings consisting of a plurality of groups of coils, each group being composed ot' a different number oi turns wound to have each a predetermined olnnicI resistance, ot a controlling switch, connectionsr between said controlling switch and said motors 'for cutting said groups of coils out successively and progressively while thc motors are in series and means lor cone necting the motors in parallel after first replacing all oit' said coils in circuit.

2.\In' sones parallel series motor control, the combination with a plurality of motors eachhaving field coils wound in groups ot' different resistances, and means for removing said groups progressivelyto increase the speed of said motors while connected in series, connecting the motors in parallel, and means -ltor then removing` said groups progressively to further increase the speed.

In series parallel series motor control, the combination with a'plurality of motors each having field coils wound in groups of dilierent resistances, and means for removing said groups progressively to increase the speed of said motors while connected in series, of means for restoring said groups and connecting the motors in parallel, means for preventing` abnormal iiow of current while changing from series toparallel, and means for then removing said groups progressively to further increase the speed.

.4. In series parallel series motor control, the combination with a plurality o'serics motors each having ield coils wound in groups oi differing resistances, and means for removing said groups progressively to increase the speed while the motors are connected in series, of means for restoring said groups and connecting the motors in parallel without opening the circuit, and means for then removing said groups progressively when connected in parallel, to further increase the speed.

5. In series parallel series motor control, the combination with a plurality of series motors, each having interpoles in series with of means tor restoring said groups yand the armature and field coils wound in groups, Y

and means for-removing said groups progressively to increase the speed and the 1nterpole magnetization while the motors are connected in series, of means for restoring said groups and connecting said motors in parallel, and means for then removing said groups progressively when connected in parallel, to still further increase the speed.

(i. The combination with a series motor having ield coils wound in groups on each pole, said groups comprising different numbers of turns and being otl dili'erent resistance, of interpoles in series with the arma,- ture and with said groups of coils, and means for cuttingsaid groups out successively and progressively whereby to vary the ield and interpole magnetization and the armature current.

ln testimony whereof I atlix my signature, in presence of two witnesses.

FRANK B. RAE.

W itnesses:

HENRY P'. Dowsr, S. W. HUMrHREY. 

